Spade, I think we are in agreement on what Augustine said, but I think I may have confused you a bit in the way I wrote it. I think this is the section you are talking about:
Augustine wrote:
“38. Let us suppose that in explaining the words, “And God said, ‘Let there be light,’ and light was made,” one man thinks that it was material light that was made, and another that it was spiritual. As to the actual existence of spiritual light in a spiritual creature, our faith leaves no doubt; as to the existence of material light, celestial or supercelestial, even existing before the heavens, a light which could have been followed by night, there will be nothing in such a supposition contrary to the faith until unerring truth gives the lie to it. And if that should happen, this teaching was never in Holy Scripture but was an opinion proposed by man in his ignorance. . . ."
And I then commented in the article:
"Here is what I think Augustine is saying here: when we read a particular text, often two people will agree that there is a particular spiritual or theological truth, based on our faith, but may differ as to whether a literal fact was meant as well. We should, then, agree on the theological truth. As for the material truth, there is nothing wrong with accepting this as well, unless and until there is evidence which shows that it can not be the true reading. When that happens, we know that the material interpretation was never part of Scripture to begin with."
As to the theological issues, we should agree, even if we do not agree on the material (literal v. figurative) issues. You and I may not agree on whether Genesis is meant to be read literally as creation in six 24 hour periods, but we can definitely agree that Genesis is telling us that God created all things, God created Man in His image, Man did something to result in a Fallen state and is in need of redemption, etc.
And then, Augustine, goes on to say that if we hold to a literal view, and then the facts come along and show that it was not meant to be literal, we should abandon that literal view without abandoning the theological points.